I try to send out cards about every 3 or 4 months. It may be overkill but in the world of Advertising it usually takes 7 attempts to get noticed. If we keep putting our names in front of the Art Directors with quality work, it will pay off.
This is the postcard I am sending out this month. I wanted to wait a bit so that the editors would be returning from vacations. My theory on this one was to present a closeup image with some added interest on the back, and make sure that even without glasses an editor would see my name and website. I have a space on the back of the card for my agent's email and phone which I put in before the cards were printed.
I have always used Overnight Prints, but may try VistaPrints at some point. Overnight gives me really good quality on a large card and this last order they gave me 50 extra cards.
And then there is MOO.com They will print 60 cards with a different image on the front of every card if you like. The price is high for 60 cards, but you can also make as few as 20 cards all with different images for $20.00. The postcards are regulation size suited for US postal conditions, but seem a bit smaller than the smallest VistaPrint or Overnight Prints cards.
They also make sticker books with as many as 90 different images. (Yes, they can also be just the same image too.) They are based in London so you need to use Pay Pal but credit cards do work. I recently ordered a book of 90 stickers for our little grandson Trevor. Some have his face; some have my illos, but all were beautifully printed! And they came in a cute little booklet. Moo has lots of goodies, you may want to take a look. They love to Print!